JPH05117854A - Preparation of article by chemical vapor deposition and supporting member used in the preparation - Google Patents

Abstract

PURPOSE: To reduce the time for etching-away and to prevent the generation of bulge and crack in an objective article by condensing an objective article onto the surface of a supporting member of a hollow structural body made of molybdenum by chemical vapor deposition and thereafter etching away the supporting member.

CONSTITUTION: Diamond thin coating 20 is vapor-deposited on the surface 18 of a supporting member 14 of a hollow structural body made of molybdenum by chemical vapor deposition. After the completion of the vapor deposition, it is charged to an etching soln., and the supporting member 14 is etched away to obtain a diamond tube 20. The time for etching-away the supporting body 14 can be remarkably reduced, and the generation of bulge and crack in the objective article 20 can be prevented.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an article by a chemical vapor deposition method, and more particularly to a diamond water heater.
The present invention relates to a support member (support mandrel) used when manufacturing a jet nozzle and a mixing tube.

[0002]

2. Description of the Related Art Diamond has an interatomic distance of 1.5.
It is an allotrope of carbon showing a crystallographic network composed exclusively of covalently bonded aliphatic sp ³ hybridized carbon atoms arranged in a uniform tetrahedral shape at 45 angstroms. Diamond is extremely hard and has a moth height of 10. It has four times the thermal conductivity of copper and is an electrical insulator. Its hardness and thermal properties are just two of the properties of diamond that are useful in various industrial parts. In the early days, natural diamonds without gem quality were used for various polishing applications, but since the invention of synthetic diamond by the high temperature / high pressure method, a series of additional products have been well received in the market. There is.
However, the requirement of high temperature and high pressure for the synthesis is a factor that prevents the widespread use of synthetic diamond.

However, as a result of accumulated industrial efforts on low pressure growth of diamond, the possibility of using diamond for various industrial applications has been dramatically opened up. Low pressure growth of diamond is referred to in the art as "chemical vapor deposition" or "CVD". This CV
For the D process, diamond grows from hydrocarbon gas at low pressure in the presence of atomic hydrogen. Many methods have already been disclosed for metastable diamond growth,
Generally, these methods differ in the method of generating atomic hydrogen, which is a key reactant, and transferring it into the system. Among those methods, the so-called "Fimelant method" uses a mixture of a gaseous carbon compound such as methane and hydrogen. This gas mixture is introduced into the substantially evacuated reaction chamber via a quartz tube located directly above the hot filament. Hydrogen from the gas mixture dissociates at the filament surface into atomic hydrogen, which then reacts with the carbon compounds to form a heated substrate (substrate).
Form condensable carbon radicals starting with elemental carbon on top.

Another method uses a plasma discharge in addition to the filament. It is believed that this plasma discharge acts to increase the nucleation density and growth rate and promotes the formation of diamond thin films rather than dispersed diamond particles. There are three basic systems in the plasma system used in such fields. One is a microwave plasma system, the second is an RF (inductively coupled or capacitively coupled) plasma system, and the third is d.
c. It is an arc plasma system.

If a free-standing diamond film is required, the substrate may be removed by conventional etching techniques such as exposing the underlying substrate to an acid for etching. For an overview of various diamond deposition methods, including the CVD method, see Bachmann et al., "Diamond Thin Films," Chemistry and Engineering News, 67th (2).
0), pages 24-39 (May 15, 1989), incorporated by reference.

[0006]

There are various problems in producing a self-supporting CVD diamond vapor deposition film. For example, to etch away a substrate, such as a solid molybdenum mandrel having a diameter of about 0.102 cm and a length of about 15.24 cm, which is the underlying layer for forming a diamond tube, 1
A long etching time of 0 days is required. In addition to this long etching time, it has also been found that reaction products formed at the interface of the removed mandrel and diamond deposited on the mandrel cause ridges and cracks in the diamond tube.

[0007]

SUMMARY OF THE INVENTION The present invention provides a support member comprising a hollow structure having an inner surface and an outer surface, the support member being used to manufacture an article by a chemical vapor deposition process. The present invention is also a method for manufacturing an article by chemical vapor deposition, wherein a gaseous mixture of hydrogen and a carbon compound is conveyed into a CVD reaction chamber, and the mixture is energized to decompose into fragments. Formed by depositing the fragments on a surface of a thermally stable hollow substrate having an inner surface and an outer surface having a shape substantially similar to the shape of the article, condensing the fragments on the surface A manufacturing method is provided in which the substrate having the article is placed in an etching bath, and the etching bath is agitated to etch away the substrate along the inner surface of the substrate to produce the article. If desired, fragments may be deposited on the inner surface of the substrate, but any portion of the inner surface should be exposed to the etchant.

[0008]

The substrate of the article is etched away along its inner surface. Other advantages of the invention will be apparent from the following detailed description, the appended claims and the accompanying drawings. For a more complete understanding of the present invention, reference may be made to the embodiments of the invention which are set forth in the accompanying drawings and the detailed description which follows.

Although the present invention is described below with reference to preferred embodiments, it should be understood that the invention is not limited to the following embodiments. On the contrary, the alternatives, modifications and equivalents are intended to be within the spirit and scope of the invention as defined by the appended claims.

[0010]

EXAMPLES Recently, the synthesis of free-standing articles made from diamond thin films has been extensively studied. One of the major problems with producing such free-standing articles is the method of removing the underlying substrate. Removal of this substrate becomes more difficult when manufacturing hollow articles such as diamond tubes used in high pressure cutting machines utilizing water jets. A preferred etching bath comprises a heated etching bath, the etching bath having a concentration in water of about 3
6 to about 38% by weight hydrochloric acid and a concentration in water of about 69 to about 71
It preferably consists of a mixture containing equal parts by weight of nitric acid and hydrofluoric acid having a concentration in water of about 49 to about 51% by weight. The etching bath is preferably heated to about 110 to about 120 ° C. Another alternative etching solution is about 69-
3 parts by weight nitric acid having a concentration of about 71% and about 36 to about 38
It consists of a mixture with 1 part by weight of hydrochloric acid having a concentration of%. However, it will be apparent to those skilled in the art to substitute other etchants that are suitably adapted to react with the substrate to be etched. The etching bath is preferably maintained at a temperature of about 5 ° C to about 10 ° C below the boiling point of the selected etchant.

The etching bath is agitated to remove bubbles formed along the surface of the substrate being etched. If this bubble is not removed from the etched surface, the etching action will stop. Therefore, the etching action is sustained by removing the bubbles. The etching bath may be subjected to ultrasonic agitation to remove bubbles. Typically, the etching time is determined according to the diffusion equation:

X ² = Dt where X is the diffusion distance (cm) and D is the diffusion coefficient of the liquid (cm
² / sec), t is the etching time (sec) required to remove the length X of the substrate by etching. However, the present invention does not rely on this diffusion equation and therefore does not rely on this equation. 1 and 2 show a prior art mandrel or support member 10 having a solid core on which a diamond tube 12 is formed by a CVD process. As can be seen from FIGS. 1 and 2, the surface on which the etching action works is the diamond tube 1.
It is difficult to etch away the solid core, as it is difficult to freely circulate the etchant over the surface to be entrapped within the tubular shape of 2 and thus to be etched.

The preferred embodiment of the present invention is a hollow mandrel or support mandrel 14 having a smooth inner surface 16 and an outer surface 18, as shown in FIGS. Outer surface 18 is typically a well-polished, polished surface. The diamond thin film 20 is formed on the outer surface 18.
It has been discovered that by using a hollow support member 14, the etching time to remove the member 14 can be significantly reduced. As shown by the arrow in FIG. 3, the etching liquid can efficiently pass along the inner surface 16 of the member 14, thereby improving the etching action. A preferred etching bath (generally designated by reference numeral 1) is shown in FIG. The etching bath 1 includes an etching solution 32 contained in an etching bath container 34.
The hollow support member 14 of FIG. 3 is preferably vertically submerged in the etchant 32. When the etching liquid 32 reacts with the metal forming the hollow support member 14, the inner surface 16 of the member 14 is
Bubbles 36 formed along and spread through the upper end of the member 14, thus inducing natural convection of the etchant 32 along the inner surface 16 of the member 14. Under such conditions ultrasonic agitation of the etchant would not be necessary. However, if desired, the etching bath 1 may be equipped with an ultrasonic stirring device 30 suitable for stirring the etching liquid 32, if desired. Another advantage of hollow member 14 over solid member 10 as shown in FIG. 1 is that less metal needs to be etched. For example, using the preferred etchant described above,
It took about 7.5 to about 10 days to etch away a prior art solid molybdenum support member having a diameter of about 0.102 cm and a length of about 15.24 cm. If this solid member is replaced with a hollow support member having the same outer dimensions as the solid member, for example, a hollow support member having a length of about 15.24 cm, a diameter of about 0.102 cm, and an inner diameter of about 0.061 cm, the etching time is about the same. It was shortened to 10 minutes. Therefore, using the hollow member 14 of FIG. 3 reduces the etching time considerably. It is also conceivable to etch and remove the hollow member 14 by connecting both open ends of the hollow member 14 to an intake pipe and an exhaust pipe through which the etching liquid flows in / out. Further, in order to simultaneously transport the etching liquid along the inner surface 16 of the series of hollow members 14, each open end of the series of hollow members 14 is connected to an inlet connection box and an outlet connection box, respectively, to improve the productivity of the etching operation. May be increased.

The present invention further provides a method for making a freestanding diamond article by a CVD process using a hollow substrate as a target for depositing a diamond film. The CVD process useful in the present invention conveys a gaseous mixture of hydrogen and a carbon compound into a CVD reaction chamber. The gaseous carbon compounds include saturated hydrocarbons such as methane, ethane and propane, and unsaturated hydrocarbons such as ethylene, acetylene and cyclohexene. It is also conceivable to use a carbon compound such as benzene in its vaporized state. However, methane is preferred. The molar ratio of hydrocarbon to hydrogen varies widely from about 1:10 to about 1: 1000, but is 1: 100.
Is preferred. This gaseous mixture may optionally be diluted with an inert gas such as argon or helium. CVD
Pressures in the chamber are in the range of about 0.01 to about 1000 Torr, preferably about 1 to about 800 Torr are common in the art.

Next, energy is applied to the gaseous mixture to decompose it into fragments. To give energy to the mixture,
The mixture is preferably passed over heated, non-reactive filaments and heated to a temperature range of about 1750 to about 2400 ° C. Such filaments are formed of tungsten, molybdenum, tantalum or alloys thereof, with tungsten being preferred. U.S. Pat. No. 4,7
No. 07,384 (incorporated) illustrates this process. Optionally, the substrate may be electron bombarded during the CVD process according to US Pat. No. 4,740,263 (incorporated).

The substrate is maintained at an elevated temperature of about 500 to about 1100 ° C, preferably about 850 to about 950 ° C. The substrate is titanium, zirconium, hafnium, vanadium, niobium,
Thermally stable metals such as tantalum, chromium, molybdenum, tungsten, manganese, rhenium, iron, rubidium, osmium, cobalt, rhodium, indium, nickel, palladium, platinum, copper, silver, gold and their alloys, carbonization It can be made of silicon, ceramics such as boron nitride, aluminum nitride, carbon (eg graphite) or silicon. Molybdenum is preferred. Unlike substrate materials such as molybdenum, some substrate materials such as chromium need to be prepared prior to diamond deposition. The preparation step is performed, for example, by adding diamond particles having a size of about 1 micron to alkane-based alcohols.
The substrate is contacted with the stirred suspension for about 5 minutes. Diamond particles with ethyl alcohol
Preference is given to suspensions which have been suspended in a flask and ultrasonically stirred. Alternatively, a suspension of diamond particles having a size of about 1 micron in a hydrocarbon oil may be rubbed onto the substrate until the surface of the substrate becomes cloudy. In the case of a thin tube-like substrate, it must be supported by a rod-like support running through it to prevent deformation of the tube during deposition of fragments along the tube's outer surface. Sometimes it doesn't. For more information on the CVD process, see Angus (Ang
(US) et al. "Low-Pressure, Metastable Growth of
Diamond and ´Diamondlike´ Phases） 」, Science
(Science), Volume 241 (August 19, 1988), pages 913-921 (incorporated by reference).

Another embodiment of the present invention is shown in FIG. The mandrel or support member 40 has a diamond film 46 deposited on its outer surface 44. The inner surface 42 has a sawtooth shape so as to promote the etching action of the etching solution 32 shown in FIG. Yet another embodiment of the present invention is shown in FIG. The mandrel or support member 50 has a diamond film 56 deposited on its outer surface 54. The inner surface 52 has a polygonal shape.

FIG. 8 shows another embodiment of the present invention. The mandrel or support member 60 has a diamond film 66 deposited on a polygonal outer surface 64. The inner surface 62 is also polygonal and forms the support member 60 having a uniform wall thickness. Yet another embodiment of the present invention is shown in FIG. The substrate 70 is spherical in shape and has an evaporated diamond thin film 76 on the outer surface 74 of the substrate 70. To etch the inner surface 72, the etchant 32 shown in FIG. 5 flows through the intake orifice 78 and the discharge orifice 80.

The present invention is applicable to, for example, a fluid nozzle, a fluid mixing tube, and a heat sink for an integrated circuit chip.
It can also be applied to the production of sinks, wire guides for electric discharge machines, yarn guides for textile machines and test tubes. In addition to diamond, the present invention can also be used for vapor deposition of silicon, germanium, boron, aluminum, zirconium, tungsten, titanium and molybdenum.

The particular embodiments described above are given by way of illustration only and should not be construed as limiting the maximum scope of the invention. Although specific embodiments of the present invention have been shown above, the present invention is limited to the above embodiments, since those skilled in the art can make modifications in light of the above teachings. Not. Accordingly, the appended claims are to be construed to cover any modification which includes essential features of the invention and which fall within the true spirit and scope of the invention.

[0021]

INDUSTRIAL APPLICABILITY In an article manufacturing method by chemical vapor deposition,
The time for etching away the support member to be vapor-deposited is greatly reduced, and at the same time, the formation of ridges or cracks in the article is prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a solid support member according to a conventional technique.

2 is a sectional view taken along line 2-2 of the conventional solid support member of FIG.

FIG. 3 is a cross-sectional view of the preferred embodiment of the present invention.

4 is a sectional view taken along line 4-4 of the preferred embodiment of FIG.

FIG. 5 is an example of an etching apparatus used for removing a support member.

FIG. 6 is a sectional view of another embodiment of the present invention.

FIG. 7 is a sectional view of still another embodiment of the present invention.

FIG. 8 is a sectional view of still another embodiment of the present invention.

FIG. 9 is a sectional view of still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Etching bath 10 Prior art mandrel or support (support mandrel) 12 Diamond tube 14, 40, 50, 60, 70 Hollow support member according to the invention 16, 72 Smooth inner surface 18, 44, 54, 74 Outer surface 20 , 46, 56, 66, 76 Diamond thin film 30 Ultrasonic stirrer 32 Etching liquid 36 Foam 42 Serrated inner surface 52, 62 Polygonal inner surface 64 Polygonal outer surface. 78 intake orifice 80 discharge orifice

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor James Fulton Flyshear Woodside Drive, 4th, Scotia, New York, USA

Claims (10)

[Claims] 1. A support member used in the manufacture of articles by chemical vapor deposition, which comprises a hollow structure having an inner surface and an outer surface. 2. The support member according to claim 1, wherein the support member is a tube having an inner surface having a smooth shape, a sawtooth shape, or a polygonal shape. 3. The support member according to claim 1, wherein the member is made of molybdenum. 4. A method for manufacturing an article by chemical vapor deposition, comprising transporting a gaseous mixture of hydrogen and a carbon compound into a CVD reaction chamber, applying energy to the mixture to decompose it into fragments, and the shape of the article. Depositing the fragments on a surface of a thermally stable hollow substrate having an outer surface and an inner surface having a shape substantially similar to, condensing the fragments on the surface, and having the article formed A method comprising placing a substrate in an etching bath and stirring the etching bath to etch away the substrate along the inner surface of the substrate to produce the article. 5. The method of claim 4, further comprising diluting the gaseous mixture with an inert gas. 6. The mixture is energized by passing the mixture over a non-reactive filament sufficiently heated to pyrolyze the mixture into fragments.
The method of claim 4, wherein 7. The method of claim 4, further comprising supporting the substrate to prevent deformation of the substrate during deposition of the fragments on the substrate. 8. The method of claim 7 wherein said substrate is a molybdenum tube supported by a rod passing therethrough. 9. The method of claim 4, wherein the article is vertically submerged in the etching bath and bubbled along the inner surface to induce convection of the etchant along the inner surface. 10. The method of claim 4, wherein the etching bath is ultrasonically agitated to remove bubbles formed along the inner surface of the substrate.